The present invention relates in general to spirodiphosphoamidate-type compounds and to a process for their preparation.
Phosphoamidate compounds have a variety of practical uses, such as flame retardants, stabilizers or intumescent agents for coatings such as paints, antitumor agents, vulcanizing agents and additives to lubricant compositions.
Spirodiphosphoamidate-type compounds, including spirodiphosphoamidates and spirodithiophosphoamidates, are known in the art. U.S. Pat. No. 3,978,167 to Albright, discloses spirodiphosphoamidate-type compounds wherein the amino moiety may be substituted with one or more hydrocarbon groups of preferably not more than about 12 carbon atoms. Albright discloses these compounds may be useful as flame retardants or pesticides. Although Albright indicates the spirodiphosphoamidate may be a dithiophosphoamidate, oxygenated diphosphoamidate-type compounds are preferred.
Other spirodiphosphoamidate-type compounds, possibly useful as anti-tumor agents, are disclosed by Chemical Abstract 70(1):4074v. Phosphoamidates, useful in lubricating compositions, are disclosed by U.S. Pat. No. 4,348,291 to Shim and U.S. Pat. No. 3,846,317 to Lintzenich. However, these compounds may not perform as well as desired in applications such as automatic transmission fluids, cutting oils, lubricating greases and hydraulic fluids wherein maintenance of good lubricating properties under extreme pressure conditions is desired.
Several processes are known for the preparation of spirodiphosphate-type compounds. U.S. Pat. No. 3,978,167 to Albright discloses the reaction of dihalo pentaerythritol phosphate with a primary or secondary amine. U.S. Pat. No. 4,154,721 to Valdiserri et al discloses the reaction of pentaerythritol with an aryl dichlorophosphine to form a diaryl spiro-disphosphonite, followed by oxidation of the diphosphonite to the corresponding diarylspirodiphosphonate. U.S. Pat. No. 4,290,976 to Hechenbleikner et al discloses a process for preparing dialkylpentaerythritol diphosphites by contacting dichloropentaerythritol diphosphite with an alcohol. U.S. Pat. No. 3,325,566 to Ratz discloses dichlorospirodiphosphite may be converted to dihydrogen pentaerythitol dithiophosphate by reaction with hydrogen sulfide. Other processes for preparing phosphoamidates and similar compounds are disclosed by U.S. Pat. No. 3,846,317 to Lintzenich and U.S. Pat. No. 3,597,503 to Wilson et al.
However, many processes for preparing spirodiphosphate type compounds have the disadvantage of fostering significant ring opening side reactions, which lower the process yield. These processes may also have the disadvantage of requiring the use of relatively high temperatures, which may further encourage formation of by-products. Therefore, a process for preparing spiroddiphosphoamidate type compounds which suppresses ring opening and may be conducted at relatively moderate temperatures offers significant practical advantages over processes known in the art.